1. Field of the Invention
The present invention relates to a method for monitoring the feed of a catalyst, especially the feed of a catalyst employed in a gas-phase linear low density polyethylene process system through the intermediary of the electro-optical scanning of an intermittent flow of the catalyst. Furthermore, the invention relates to an apparatus for monitoring the catalyst feed in a gas-phase linear low density polyethylene process for the implementing of the inventive monitoring method.
Quite frequently, catalyst feed systems which are employed in gas-phase linear low density polyethylene processes and systems evidence a tendency to plug as to inhibit catalyst flow, or may, at times, fail to uniformly convey catalyst to the reactor which is utilized in the process. Such disruptions or undesirable fluctuations in the catalyst feed often necessitate the passage of hours of process reaction time before the poor feed conditions in the catalyst feed systems become evident in the LLDPE process; for instance, as may be indicated by a reduced reaction rate of the process. The problem is particularly troublesome during start-ups of the process system and reactor apparatus, at which point in time it is extremely difficult to precisely diagnose the cause of the reduced reaction rate of the process, inasmuch as numerous other causes can adversely affect or even completely inhibit initiation of the desired process reaction. Consequently, in order to enhance the economics and operating efficiency of such a process in determining the appropriate catalyst feed conditions for a gas phase LLDPE process system or reactor, it is of particular advantage to be able to incorporate a monitoring method and apparatus in the process which, almost instantaneously, will provide appropriate and rapid information as to whether the catalyst flow and feed into the LLDPE process system is being implemented at an appropriate feed rate and timing.
In order to achieve the foregoing, the present invention contemplates the utilization of a method and apparatus for monitoring the catalyst feed in a gas-phase linear low density polyethylene process, in which an intermittent flow of the catalyst, which is generally opaque, is monitored through the utilization of fiber optics and a light source and light detector device, wherein light which is conducted through the fiber optics passes through a clear or transparent flow channel through which there is effected the catalyst flow, and is monitored through a suitable photocell. The catalyst particles will interrupt the light beam while traversing the transparent flow channel and allow this to be registered by the photocell on a suitable indicating instrument.
2. Discussion of the Prior Art
Although numerous devices are presently known in the technology which employ methods for the electro-optical scanning of various materials, none of these devices and methods are directly applicable to the inventive method of monitoring the feed or flow of a generally opaque catalyst utilized in a gas-phase linear low density polyethylene process.
Kapany, et al. U.S. Pat. No. 3,255,357 discloses an arrangement for scanning imprinted graphical information on a continuously moving transparent tape by the projection therethrough of light through the intermediary of light-conducting optical fibers. The changes in the intensity of the light transmitted by the optical fibers upon passage through the continuously moving tape provides information over data imprinted on the transparent tape.
Pearson U.S. Pat. No. 1,849,881 discloses an apparatus for transmitting a beam of light through a continuously moving web of a substantially translucent material, such as paper, cloth or film, or liquids retained between generally flat glass plates or walls, and is employed to measure the light transmitting properties thereof. In this instance, the apparatus and method disclosed by Pearson is not readily applicable to a catalyst feed monitoring system in a gas-phase linear low density polyethylene process in which the catalyst is fed through a transparent flow secgtion in intermittent slugs or charges past the electro-optical or fiber optics scanning arrangement.
Ponghis, et al. U.S. Pat. No. 3,718,758 relates to an optical arrangement and method for monitoring the operation of a furnace, such as a blast furnace, in which a light conductor provides for the visual examination of the furnance charge, and of the walls and accessories of the furnace. This arrangement also is clearly inapplicable to the measurement and monitoring of an intermittent feed of a generally opaque catalyst in a gas-phase linear low density polyethylene process system.
Piepenbrink, et al. U.S. Pat. No. 3,317,738 discloses a photoelectric scanning arrangement in which a light conducting rod with a fluorescent portion is adapted to reflect light through the wall of a flow conduit in order to provide information with regard to the degree of opaqueness of a fluid which is conveyed through the conduit, and with regard to a material web adjacent a roller structure. This will enable an optical inspection to be effected for the presence of any holes, perforations or texture flaws in webs, contributed, for example of paper, metal foil, leather and the like. In this case, as in the other prior art discussed hereinabove, none of the scanning or monitoring methods and arrangements are adapted to provide for an electro-optical indication and information relative to the intermittent feed of a generally opaque catalyst employed in a gas-phase linear low density polyethylene process system.
Finally, Day U.S. Pat. No. 3,036,153 discloses an electro-optical scanning system for testing the opaqueness of various objects through the intermediary of light-transmitting optic fibers, wherein any variations in the degree of opaqueness or translucency are transmitted to a suitable receiver for information and evaluation. Also, in this instanace is there no particular application of such a system to the monitoring of intermittent of feed catalyst charges utilized in the gas-phase of a linear low density polyethylene process system.